Map of Gen. Taylor’s advance, July 1845 to May 1846.
On this date, the U.S. Congress overwhelmingly voted in favor of President James K. Polk’s request to declare war on Mexico in a dispute over Texas – the first American military conflict fought entirely on foreign soil.
The events that led to the war show that Polk deliberately provoked the conflict: Although Mexico had not formally recognized the independence of Texas or its annexation by the United States, Polk ordered General Zachary Taylor in 1845 to lead a 3,500-man army into Texas to Corpus Christi on the Nueces River, which Mexico considered its northern border.
On 8 March 1846, Secretary of War Marcy ordered Taylor to move his army from Corpus Christi to the Rio Grande River, which Texas considered its southern border. On March 28, Taylor reached his destination, the north bank of the river directly opposite the Mexican town of Matamoros. His army began constructing an earthen fortification called Fort Texas (later renamed Fort Brown).
On April 11, Mexican General Mariano Arista and his army reached Matamoros. Arista considered Taylor’s arrival on the Rio Grande an act of aggression and demanded that his army withdraw north of the Nueces River, but Taylor refused. Mexican President Mariano Paredes issued a manifesto on April 23, arguing that by advancing into Mexican territory — and simultaneously threatening Upper California with naval mobilizations off the Pacific Coast — the United States had already begun hostilities. Mexican soldiers believed it was a defensive war when they ambushed the troops of American Captain Seth B. Thornton and killed or injured about 16 of his men on April 24; Taylor sent Polk a letter declaring that “hostilities have commenced.”
Interestingly, on 12 January 1848, a member of the Illinois delegation to the U.S. House of Representatives, Abraham Lincoln, questioned Polk’s motives and accused him of lying to Congress about his justification for the war:
The President, in his first message of May, 1846, declares that the soil was ours on which hostilities were commenced by Mexico; and he repeats that declaration, almost in the same language, in each successive annual message – thus showing that he esteems that point a highly essential one. In the importance of that point, I entirely agree with the President. To my judgment, it is the very point upon which he should be justified or condemned. In his message of December, 1846, it seems to have occurred to him… that it was incumbent upon him to present the facts from which he concluded the soil was ours, on which the first blood of the war was shed. Accordingly…in the message last referred to, he enters upon that task; forming an issue and introducing testimony… Now, I propose to try to show that the whole of this — issue and evidence — is, from beginning to end, the sheerest deception.
I am now through the whole of the President’s evidence; and it is a singular fact, that if any one should declare the President sent the army into the midst of a settlement of Mexican people, who had never submited, by consent or by force to the authority of Texas or of the United States, and that there, and thereby, the first blood of the war was shed, there is not one word in all the President has said which would either admit or deny the declaration [i.e., Polk did not answer the charge]. In this strange omission cheifly consists the deception of the President’s evidence – an omission which, it does seem to me, could scarcely have occurred but by design. [emphases in the original]
An important factor that led to the war was the American ideology of Manifest Destiny. John L. O’Sullivan coined the phrase when he wrote in the July/August 1845 issue of The Democratic Review that it must be “our manifest destiny to overspread the continent allotted by Providence for the free development of our yearly multiplying millions.” The term conveyed the idea that the rightful destiny of the United States included imperialistic expansion.
Although the phrase Manifest Destiny was a neologism in 1845, the philosophy it referred to had been around for centuries in America. As originally conceived, Manifest Destiny was an unabashedly prejudiced idea. It rested upon the sidelining or eradication (both real-world and fictional) of American Indian peoples; there was little place for African Americans (free or enslaved) within the trope; Asian and Hispanic immigrants did not figure in the ideal America it conjured. Catholics were generally ignored; women were deemed unimportant. God intended North America to be under the control of peoples who were white, Protestant, and overwhelmingly male, with an unquenchable thirst for free enterprise. It was a kind of early projection of Anglo-Saxon supremacy and there was a conspicuous racist element to it.
Boone’s First View of Kentucky, by William Ranney (1849). Manifest Destiny influenced American art, and American art supported Manifest Destiny.
Of course, Americans did not universally subscribe to Manifest Destiny, but its vocal critics were always in the minority. One of them, William E. Channing, wrote an open letter to Henry Clay in 1837:
Did this county know itself, or were it disposed to profit by self-knowledge, it would feel the necessity of laying an immediate curb on its passion for extended territory…. We are a restless people, prone to encroachment, impatient of the ordinary laws of progress… We boast of our rapid growth, forgetting that, throughout nature, noble growths are slow….. It is full time that we should lay on ourselves serious, resolute restraint. Possessed of a domain, vast enough for the growth of ages, it is time for us to stop in the career of acquisition and conquest. Already endangered by our greatness, we cannot advance without imminent peril to our institutions, union, prosperity, virtue, and peace….. It is sometimes said, that nations are swayed by laws, as unfailing as those which govern matter; that they have their destinies; that their character and position carry them forward irresistibly to their goal;….that … the Indians have melted before the white man, and the mixed, degraded race of Mexico must melt before the Anglo-Saxon. Away with this vile sophistry! There is no necessity for crime. There is no fate to justify rapacious nations, any more than to justify gamblers and robbers, in plunder. We boast of the progress of society, and this progress consists in the substitution of reason and moral principle for the sway of brute force….We talk of accomplishing our destiny. So did the late conqueror of Europe [Napoleon]; and destiny consigned him to a lonely rock in the ocean, the prey of ambition which destroyed no peace but his own.
I have alluded to the want of wisdom with which we are accustomed to speak of our destiny as a people. We are destined [emphasis in the original] (that is the word) to overspread North America; and, intoxicated with the idea, it matters little to us how we accomplish our fate. To spread, to supplant others, to cover a boundless space, this seems our ambition, no matter what influence we spread with us. Why cannot we rise to noble conceptions of our destiny? Why do we not feel, that that our work as a nation is, to carry freedom, religion, science, and a nobler form of human nature over this continent; and why do we not remember, that to diffuse these blessings we must first cherish them in our own borders; and that whatever deeply and permanently corrupts us will make our spreading influence a curse, not a blessing, to this new world? It is a common idea in Europe, that we are destined to spread an inferior civilization over North America; that our slavery and our absorption in gain and outward interests mark us out, as fated to fall behind the old world in the higher improvements of human nature, in the philosophy, the refinements, the enthusiasm of literature and the arts which throw a lustre round older countries. I am not prophet enough to read our fate. I believe, indeed, that we are to make our futurity for ourselves. I believe, that a nation’s destiny lies in its character, in the principles which govern its policy and bear rule in the hearts of its citizens. I take my stand on God’s moral and eternal law. A nation renouncing and defying this cannot be free, cannot be great.
After the Mexican-American War began, U.S. expansionists invoked the phrase Manifest Destiny to rationalize imperialistic demands that their country use the opportunity provided by the conflict and conquer and retain much or all of Mexico. Even O’Sullivan, who had stressed Manifest Destiny’s peaceful nature, claimed that the United States deserved an indemnity such as California from Mexico. Many wartime proponents of Manifest Destiny fused into the ideology a belief that the United States had a mission to regenerate Mexico by bringing progress and Protestantism southward: U.S. troops would liberate what was described as a benighted Mexican population from the control of despotic rulers and Catholic priests. In answer to racist objections to absorbing Mexicans into the Union, some wartime expansionists responded that through superior breeding abilities or other means U.S. Anglo-Saxons would gradually displace Mexicans, and that there was nothing to fear from expansion southward.
Manifest Destiny was a graceful way to justify something unjustifiable. Ulysses S. Grant, one of the most prominent of American military men, and himself a participant in the war, wrote in his memoirs, “I do not think there ever was a more wicked war than that waged by the United States in Mexico. I thought so at the time, when I was a youngster, only I had not moral courage enough to resign.”
Unfortunately, the ideology of Manifest Destiny has continued to be an important concept in American culture up to the present day. After the Mexican-American War, U.S. expansionists broadened Manifest Destiny’s scope, applying the slogan increasingly to areas beyond the continent including Cuba, Hawaii, South America, and the Philippines. Like Americans before 1845, we may not use the specific words “Manifest Destiny” to describe the belief that America has a unique destiny in the world, but the concept is still at the heart of much U.S. foreign policy, American pop culture, and contemporary political debate.